This invention relates to the repair of articles made of gamma titanium aluminide alloys, and more particularly, to repair by a combined welding and brazing approach.
Titanium aluminides are a class of alloys whose compositions include at least titanium and aluminum, and typically some additional alloying elements such as chromium, niobium, vanadium, tantalum, manganese, and/or boron. The gamma titanium aluminides are based on the gamma phase found at nearly the equiatomic composition, with roughly 50 atomic percent each of titanium and aluminum, or slightly reduced amounts to permit the use of other alloying elements. The titanium aluminides, and particularly the gamma titanium aluminides, have the advantages of low density, good low and intermediate temperature strength and cyclic deformation resistance, and good environmental resistance.
Gamma titanium aluminides can be used in aircraft engines. They potentially have applications such as low-pressure turbine blades and vanes, bearing supports, compressor casings, high pressure and low pressure hangars, frames, exhaust nozzle flaps, diffusers, and low pressure turbine brush seal supports. They may also have application in other products such as automotive valves and superchargers.
Articles made of gamma titanium aluminide alloys are usually cast from the melt into a mold, with investment casting being the most popular approach, and then further processed. The as-cast articles sometimes have surface defects such as hot tears and surface-connected porosity due to shrinkage defects. These surface defects are deleterious to the properties of the article, either directly or by preventing the closure of interior porosity and shrinkage cavities during subsequent processing.
If the surface defects are not too severe, as is often the case, they may be repaired. However, existing repair techniques are not fully satisfactory in removing the surface defects. The inventors have recognized a need for an improved technique for repairing surface defects in gamma titanium aluminide articles. The present invention fulfills this need, and further provides related advantages.